Dynamo-electric machine.



I Patented May 4, 1909 H RM um. T m EE VU NN E U M J ATTY.

GGERATH.

DYNAMO TRIC MACHINE. APPLICATION FILED JULY NOE ELEG

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UTTEB STATES PATENT OFFIQE.

JAKOB E. NOEGGERATH, OF SGHENEOTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

DYNAMO-ELEC'IRIC MACHINE Specification of Letters Patent.

Patented May 4, 1909.

Application filed Ju1y'23, 1908. Serial No. 444,881.

big speeds. Furthermore, a comparatively large number of brushes must beemployed to collect the current induced in the armature. If readilyvolatilized metal were used for collector-rings or brushes, the wear onthis large number of brushes would be great. I, consequently, prefer, asdisclosed in prior applications, to employ collector-rings of metalwhich does not readily volatilize, as, for instance, steel, with brushescomposed partly of similar metal and partly of hi hly conducting metalsuch as copper. These brushes may be .constructedof laminae, partly ofcopper and partly of steel. The copper laminae give the brushes highconductivity, while the steel laminae reduce they wear on the brushes.

I have discovered that if the collectorrings are made of steeland-thebrushes are partly composed of steel laminae, a very considerablestray flux asses through the collector-rings and brus es due to thecompare tively 10W magnetic reluctance of this path.

' brush; and consequently Tl'fis flux shifts its position in thecollectorrings, as the armature revolves and diilerent parts of the ringare bropght beneath the dy-currents are induced in the collector-rings,which result in heating losses materially affecting the efficiency ofthe machine.

One feature of my invention consists in providing means for preventingor reducing the stray flux, which produces these losses. I accomplishthis by providing coils arranged magnetic material in the path of theflux to produce a magnetomotive force opposing a stray .flux assingthrough collector-ring and brush. acli coil may surround the ath of thestray flux through a number of lirushes, or each coil may surround asingle brush.

; As a further means of reducing stray fluxes andresultant licatinglosses, I introduce nonunilpolar machines, they must bedriven atpassingthrough collector-ring and brush. To reduce the eddy current losses inthe collector rings due to the reversal of current in them as they passunder the brushes, which losses would otherwise be appreciable becausethe rings are of magnetic material, I provide the rings with a strip ofhi hly conducting material such as copper, which carries most of thecurrent and is shaped so that the flux in the collector ring is madecomparatively small.

A further feature of my invention consists in so distributing thevolatile and non-volatile material in the brushes as to obtain a moreeven wear, than would be the case if all the brushes were similarlyconstructed. For a given brush'construction, the amount of wear variesaccording to the polarity of the brush, the wear being greater where thecurrent flows from brush to ring. The wear is thus greater at thenegative brushes of a genorator and-at the ositive brushes of a motor. Iaccording y form those brushes, through which current flows to thecollectorrings, with a greater proportion ofsteel and a smallerproportion of copper than the brushes at the'other end the machine.

My invention will best be understood by reference to the accompanyingdrawings, in which Figure '1 shows a portion of a unipolar machine havina coil for o posing a stray flux. through 1; e brushes; 1g. 2 shows amodified structure of the coil; Fig. 3 shows diagrammatically thedifferently constructed brushes at opposite ends of the machine; Figs. 4and 5 are cross-sections of the col lector-rings on the lines 4-4 and5-5 of Fig. 1, respectively; and Figs. 6, 7 and 8 show modifiedconstructions.

Inthe drawings, A represents a collectorring, which is supported on thearmature periphery (not shown) by studs (1 a.

B represents brushes bearing on the collector-rlng. These brushes arecarried by brush-holders C, which extend through apertures in the fieldmagnet D, which apertures are provided to ailord easy access to thebrushes. It willbe seen from Fig. 1

that if the collector-ring is of steel, the

brushes B com osed partly of steel lamina, and the brush olders O ofmagnetic material, t a path of comparatively low reluctance isaffordedthrough collector-ring and brushes for a stray flux passing fromthe armature'to thefieldmagnet, and that this Itis not necessary thatthe coils for opposing the stray flux should each surround a pluralityof brushes; instead, coils e may be employed as shown in Fig. 2, eachsurrounding a single brush. It has been said" that the brushes arecomposed of copper and steel laminae. I have also said that it isdesirable to employ a greater proportion of steel in those brushes fromwhich current fldws to the collector-ring. Such an arrangement isindicated diagrammatically in Fig. 3, in which E represents an armatureconductor connected at its opposite ends to, collector-rings. Thedirection of current in the conductor is indicated by anarrow, and alsob the plus and minus signs applied to the co lector-rings. The copperlaminae are indicated by b and the steel laminae by b. It will beseenthat the brush in engagement with the negative collector-ring iscomposed more largely of "steel than the other brush.

. By this difference in their material, the wear on ghe two brushes isapproximately equal ize In addition to, or in lace of, the coils foropposing a stray flux t rough the brushes,

non-magnetic material may be introduced in the path of this stray flux.This may take the form of non-magnetic supporting studs 0,, for thecollector-rings and co per strips F sheathing the inner periphery o therings.

These strips also reduce the losses due to eddy currents produced in therings by reversal of current therein under the brushes, since thestrips, being of high conductivity, carry most of the current and may'be so shaped as to give a long path in air g t any flux surrounding thestrip, so that the amount of flux in the collector rings is madecomparatively small. Suitable shapes for the strips are indicated inFigs. 6, and 8. In Fig. 6 the width of the strip F 1s innot bent down.

creased, and its edges bent down to form flanges extending away from thecollector.- ring so that the path in air of a flux surrounding the stripis comparatively long. In Fig. 7 the strip F is widened, but its edgesare In Fig. 8 the strip is widened and also has a depending centralflange. Since these strips greatly reduce the flux in thecollector-rings, they greatly reduce the eddy current losses due tocurrent reversal .in the rings.

I do not desire to limit myself to" the particular construction andarrangement of parts here shown,fbut aim in the a 'nded Within the scopeof my invention. i

What I claim as new and desire to secure byLetters Patent of the UnitedStates, is,

-1. In a d amo-electric machine, collec: tor-rings an brushes bothhaving ma etic material in their composition, and co arranged to producea magnetomotive force opposing a stray flux passing throughcollector-rings and brushes.

2. In a d amo-electric machine, collector-rings an brushes both havinmagnetic material in their composition, anfi coils surrounding the path0 a stray flux passing throu h said brushes. 3. In a dynamo-electricmachine, collector-rings of magnetic material, a magnetic fieldstructure provided with apertures, brush-holders extending through saida ertures, brushes having ma etic materi in their composition carrie bysaid brush holders and engaging said collector-' s,

and coils surrounding said apertures on t e "claimsto cover allmodifications w 1chtfgare' doctors having a greater proportion of hardmetal'than the brushes at the other end.

5. In a dynamo-electric machine, armature conductors connected at bothends to collector-rings, and brushes engaging said rings composed oflaminae of hard and soft metals, the hard metal laminae composing agreater part of the brushes at one end of the conductors than of thebrushes at the other 6. In a dynamo-electric machine, collector-ringsand brushes both having magnetic material in their composition, andmembers of nonmagneti'c 5 material inserted in the ath of a stray fluxpassing through rings and rushes.

7. In. a dynamo-electric machine, collec- I tor-ringsancl brushesbothhaving magnetic a material in their composition, and highly conductingmembers of non-magnetic material inserted in the path of a stray fluxpassing through said rings.

8. In a dynamo-electric machine, collector-rings and brushes both-havingmagnetic material in their composition, and a sheathing of highlyconductin non-magnetic material on the inner side 0 said rings.

9. In a dynamo-electric machine, collector-rings ha ving magneticmaterial in their I rings shaped to' give a, long Fath through aircomposition, and strips of highly conductin for a flux surrounding one 0said strips. 10 non-magnetic material in contact with sai( In witnesswhereof, I have hereunto set my rings. 1 hand this 21st dag of July,1908. 0 10. In a dynamo-electric machine, collec- JAK B NOEGGERATH.

tor-rings having magnetic material in their Witnesses: composition, andstrips of highly conductin BENJAMIN B. HULL, non-magnetic material incontact with sai HELEN ORFORD.

